This invention relates to the reaction and recovery of products in a hydrogen fluoride (HF) catalyzed alkylation. In one of its aspects, this invention relates to the contact of isoparaffin with olefin in the presence of HF catalyst to produce alkylate product. In another of its aspects, this invention relates to the supplying of energy for the separation of the reaction products of an alkylation process.
Various schemes have been proposed to maximize the efficiency of energy use in the separation of the components of the effluent from various chemical reactions. Some reactions, such as the contact of isoparaffin with olefin in the presence of an HF catalyst to produce an alkylate product, produce an effluent that contains a variety of components that can be profitably separated as salable product or for recycle into the reaction process. Since the reaction effluent also contains impurities which can be harmful to the salability of the product or to the efficiency of the reaction the removal of these impurities also becomes an important factor to consider in the treatment of the reaction effluent. Effluent treatment is a multi-faceted problem which lends itself to a variety of solutions.
In the present invention use is made of a flashing operation to reduce the load of low boiling fraction from the kettle of a first fractionator that is passed to a second high pressure, high temperature fractionator. This operation allows the use of a smaller second fractionator, i.e., less trays in the fractionator. For further energy and equipment economies the hot overhead from the high pressure, high temperature fractionator can be passed into indirect heat exchange with the bottoms fraction leaving the first fractionator to increase the temperature of the stream before it is flashed thereby causing more of the low boiling material to flash and even less material to be passed as feed to the high pressure, high temperature fractionator.
It is therefore an object of this invention to provide a method for separating isoparaffin from the hydrocarbon phase of an alkylation reactor effluent which economizes both in equipment and energy usage. It is another object of this invention to provide a system for heat exchanging product and feed streams in a recovery system utilizing two fractionation columns in series to provide a system in which less material needs to be treated in the second fractionator. It is still another object of this invention to provide a method for treating the overhead from a fractionator containing isoparaffin, HF, and organic fluoride impurities so that the organic impurities are removed.
Other aspects, objects and the various advantages of this invention will become apparent upon reading this specification and the appended claims.